In recent years, treatment of a site on which it is difficult to perform a surgical operation, for example, percutaneous transluminal coronary angioplasty (PCTA), or treatment for minimum invasion into a human body has been performed using a catheter. In such a treatment, a guide wire is percutaneously inserted into a biological lumen, for example, a blood vessel, a catheter is pushed along the guide wire while the guide wire is advanced, and a distal portion of the catheter is induced to a target site, to perform treatment using a catheter. Accordingly, it can be necessary for the catheter to be flexibly bent along the shape of the lumen in the biological lumen. For this reason, a method (for example, refer to JP-T-2010-527258) of forming a spiral slit on an elongated tubular body constituting a shaft of a catheter has been known for the purpose of increasing flexibility of the catheter.
However, when a spiral slit is formed on a tubular body constituting a shaft of a catheter, torque transmission performance in accordance with a rotational direction varies due to anisotropy of the structure, and therefore, the operability of the catheter can be reduced. For example, torque acts in a direction, in which the gap of the slit is closed, when a proximal portion of a catheter is rotated on one direction side, whereas torque acts in a direction, in which the gap of the slit is opened, for example, a direction, in which the spiral is released, when the proximal portion of the catheter is rotated on the opposite direction side thereof. Slits cannot be closed more than the width of the gap of the slit in a case where torque acts in the direction in which the gap of the slit is closed, and therefore, the torque can be favorably transmitted. In contrast, the gap of the slit is opened more than necessary in a case where torque acts in a direction in which the gap of the slit is opened, and therefore, the torque cannot be favorably transmitted, thereby easily reducing the operability.